Republican presidential candidate and former Massachusetts Gov. Mitt Romney holds up a "presidential accountability scorecard" comparing himself to President Barack Obama, as he campaigns Thursday at the Jefferson County Fairgrounds in Golden, Colo. (ASSOCIATED PRESS / Charles Dharapak)

GOLDEN, Colo. (AP) — Mitt Romney promised Thursday that his economic program will create 12 million new jobs in the next four years, and likened President Barack Obama to a “dog trying to chase its tail” when it comes to strengthening the sluggish recovery.

Firing back instantly, Obama said his rival favors “trickle-down fairy dust” that has failed to fix the economy in the past, and unleashed a new television ad with a scathing summation of Romney’s tax plans: “He pays less. You pay more.”

The two men campaigned in battleground states hundreds of miles apart, the incumbent in Florida, his challenger in Colorado, both on a mission to convert undecided voters to their side in a race dominated by the economy and high joblessness.

Nor was there any summer lull in the television ad wars. Americans For Prosperity, an independent group that backs Romney, intends to launch a $25 million ad campaign beginning next week, according to officials familiar with the arrangements. The organization was founded by David and Charles Koch, billionaire brothers, and has spent about $15 million in swing states this year on ads attacking Obama.

For Romney, the day meant a return to domestic campaigning after a weeklong overseas trip. Aides say he intends to disclose a vice presidential pick before the Republican National Convention opens on Aug. 27 in Tampa, Fla., but the former Massachusetts governor told reporters: “I’ve got nothing to give you” by way of information on his decision.

Instead, he unveiled what aides called Romney’s plan for more jobs and more take-home pay, backed by an eight-page paper arguing that the economic stimulus and other policies backed by Obama “exacerbated the economy’s structural problems and weakened the recovery ... At the present rate of job creation, the nation will never return to full employment,” it said, on the eve of the release of the government’s official report on July joblessness.

Following the release of Friday’s jobs report, Obama planned to use the backdrop of the White House and surround himself with families who would benefit from the election year middle-class tax cut he’s pushing Congress to adopt. “As dysfunctional as Washington can be, this fight is far from hopeless,” White House senior adviser David Plouffe said in an email.

In remarks in Golden, Colo., Romney said his economic policies would lead to creation of 12 million jobs in the four years of his term, if he is elected, and help make North America energy independent, a pledge that aides said included Canada and Mexico as well as the United States.

Romney pledged expanded international trade, particularly with Latin America, and vowed to confront China over its own policies. “I’m finally going to sit down with the Chinese and they’re going to understand that if they cheat there are going to be consequences, because we’re not going to let them walk all over us,” the former Massachusetts governor said.

He said he would help small business owners, improve the education system and cut spending to reduce the deficit, but he offered relatively few specifics.

Romney previously has said he wants to extend the tax cuts due to expire on Dec. 31 and grant a new 20 percent cut in tax rates, in addition, to stimulate growth. He has also said he will reverse some of Obama’s proposed defense cuts, and simultaneously reduce spending on other programs in a way that deficits would gradually subside.

But he so far has refused to identify which existing tax breaks he would curtail to accomplish his goals, and generally avoided naming individual programs he wants to cut or eliminate.

In his remarks during the day, Romney said he wants federal education funds that aid the disadvantaged and disabled to be tied to the student rather than flow to school districts, as is now the case. But he did not specify how much he would cut from them to achieve his goal of reducing federal deficits.

He also criticized Obama for signing legislation that cut $500 billion from Medicare over a decade. Aides said he would restore the funding, which was reduced as part of the president’s health care bill. But they had no additional details.

Romney said Democrats have a different view. “They think we should just raise taxes. ...The problem is when you raise taxes you lower growth,” he said.

Obama’s approach is “like a dog trying to chase its tail, you just don’t ever get there,” he added. “So the right answer is not to raise taxes. The right answer is to cut taxes and cut spending.”

Obama and other Democrats support extending existing tax cuts except for individuals making more than $200,000 a year and couples with incomes over $250,000 — and their disagreement with Romney and the Republicans on this point has emerged as arguably the most fundamental one of the campaign.

It’s an argument that Obama seems eager to have — using campaign appearances and paid television advertising to do so.

For the second day in a row, Obama cited a study by the nonpartisan Tax Policy Center that says Romney and other millionaires would receive a tax cut of approximately $250,000 a year if the former Massachusetts governor gets his way.

“In order to afford just one $250,000 tax cut for someone like Mr. Romney, 125 families like yours would have to pay another $2,000 in taxes every year,” Obama told a crowd later in Leesburg, Va., to supportive shouts of “Not fair!”

The president’s new campaign ad was delivering the same highly personalized message. It says Romney has paid a lower proportion of his income in taxes than many people of lesser means and adds:

“He pays less, you pay more,” the ad says.

Romney’s personal wealth has been estimated as high as $250 million, but he has not so far made public a detailed disclosure of his holdings. His aides have sought to dismiss the report as a partisan attack by former aides to the president.

But Obama, picking up on what his own campaign staff said Wednesday, told an audience near Orlando, Fla., that the Tax Policy Center was headed by a former aide to President George W. Bush.

Romney, too, rolled out a new ad, giving a less-than-warm welcome to Obama on a day Air Force One touched down in Florida. It notes that the state still suffers from high unemployment, record home foreclosures and an increase in poverty.

“Barack Obama: What a disappointment,” it says.

The president’s stop in Florida reflected his campaign’s efforts to build support among Hispanic voters, particularly Puerto Ricans. He was greeted on the tarmac of Orlando International Airport by Kenneth McClintock, the lieutenant governor of Puerto Rico and Alejandro Garcia-Padilla, a state senator in Puerto Rico.

Romney, meanwhile, appeared with a group of Republican governors at an event near Aspen, Colo., some of them mentioned as potential running mates. That teased speculation about Romney’s vice presidential pick, as some of the attendees — New Jersey’s Chris Christie, Louisiana’s Bobby Jindal, South Carolina’s Nikki Haley and Virginia’s Bob McDonnell — have been mentioned as possible Romney running mates.

Each of the governors briefly addressed the crowd after Romney spoke, giving the setting the feel of a tryout of sorts as Romney, hundreds of supporters and the national media watched closely.

Haley was among the most aggressive, promising to fight to help get Romney elected: “I know when we have Gov. Romney, someone’s going to have our back,” she said.